Quick example of registering a URLScheme in a Titanium app using the TiApp.xml without info.plist file. Just add the following into your TiApp.xml (I put it under the </iphone> tag. Works on Android and iOS.

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Quick Example of registering a scheme in TiApp.xml, implementing the code in app.js / alloy.js

app.js

// points for getting this shorter using regex
function urlToObject(url) {

  var returnObj = {};

  url = url.replace('URLSCHEMENAME://?', '');

  var params = url.split('&');

    params.forEach(function(param) {
                  
      var keyAndValue = param.split('=');
    
      returnObj[keyAndValue[0]] = decodeURI(keyAndValue[1]);
  
    });

  return returnObj;
}

function processArgs() {
  if (Ti.App.getArguments().url) {     
          urlToObject(Ti.App.getArguments().url);
  }  
}

// on launch
processArgs();

// on resume
Ti.App.addEventListener("resumed", function(){
  processArgs();
});

TiApp.xml

<ios>
      <plist>
            <dict>
                <key>CFBundleURLTypes</key>
                <array>
                    <dict>
                        <key>CFBundleURLName</key>
                        <string>com.yourdomain.yourappprefix</string>
                        <key>CFBundleURLSchemes</key>
                              <array>
                                    <string>URLSCHEMENAME</string>                           
                              </array>
                    </dict>
                </array>
            </dict>
      </plist>      
</ios>
 <android xmlns:android="http://schemas.android.com/apk/res/android">
        <activities>
            <activity url="app.js"
            android:launchMode="singleTask" android:alwaysRetainTaskState="true">
                <intent-filter>
                    <action android:name="android.intent.action.VIEW"/>
                    <category android:name="android.intent.category.DEFAULT"/>
                    <category android:name="android.intent.category.BROWSABLE"/>
                    <data android:host="" android:scheme="URLSCHEMENAME"/>
                </intent-filter>
            </activity>

        </activities>
    </android>